<?php

/**
 * @file
 * Query code for SQLite embedded database engine.
 */

/**
 * @ingroup database
 * @{
 */

/**
 * SQLite specific implementation of InsertQuery.
 *
 * We ignore all the default fields and use the clever SQLite syntax:
 *   INSERT INTO table DEFAULT VALUES
 * for degenerated "default only" queries.
 */
class InsertQuery_sqlite extends InsertQuery {

	public function execute() {
		if (!$this->preExecute()) {
			return NULL;
		}
		if (count($this->insertFields)) {
			return parent::execute();
		}
		else {
			return $this->connection->query('INSERT INTO {' . $this->table . '} DEFAULT VALUES', array(), $this->queryOptions);
		}
	}

	public function __toString() {
		// Create a sanitized comment string to prepend to the query.
		$comments = $this->connection->makeComment($this->comments);

		// Produce as many generic placeholders as necessary.
		$placeholders = array_fill(0, count($this->insertFields), '?');

		// If we're selecting from a SelectQuery, finish building the query and
		// pass it back, as any remaining options are irrelevant.
		if (!empty($this->fromQuery)) {
			return $comments . 'INSERT INTO {' . $this->table . '} (' . implode(', ', $this->insertFields) . ') ' . $this->fromQuery;
		}

		return $comments . 'INSERT INTO {' . $this->table . '} (' . implode(', ', $this->insertFields) . ') VALUES (' . implode(', ', $placeholders) . ')';
	}

}

/**
 * SQLite specific implementation of UpdateQuery.
 *
 * SQLite counts all the rows that match the conditions as modified, even if they
 * will not be affected by the query. We workaround this by ensuring that
 * we don't select those rows.
 *
 * A query like this one:
 *   UPDATE test SET name = 'newname' WHERE tid = 1
 * will become:
 *   UPDATE test SET name = 'newname' WHERE tid = 1 AND name <> 'newname'
 */
class UpdateQuery_sqlite extends UpdateQuery {
	/**
	 * Helper function that removes the fields that are already in a condition.
	 *
	 * @param $fields
	 *   The fields.
	 * @param QueryConditionInterface $condition
	 *   A database condition.
	 */
	protected function removeFieldsInCondition(&$fields, QueryConditionInterface $condition) {
		foreach ($condition->conditions() as $child_condition) {
			if ($child_condition['field'] instanceof QueryConditionInterface) {
				$this->removeFieldsInCondition($fields, $child_condition['field']);
			}
			else {
				unset($fields[$child_condition['field']]);
			}
		}
	}

	public function execute() {
		if (!empty($this->queryOptions['sqlite_return_matched_rows'])) {
			return parent::execute();
		}

		// Get the fields used in the update query, and remove those that are already
		// in the condition.
		$fields = $this->expressionFields + $this->fields;
		$this->removeFieldsInCondition($fields, $this->condition);

		// Add the inverse of the fields to the condition.
		$condition = new DatabaseCondition('OR');
		foreach ($fields as $field => $data) {
			if (is_array($data)) {
				// The field is an expression.
				$condition->where($field . ' <> ' . $data['expression']);
				$condition->isNull($field);
			}
			elseif (!isset($data)) {
				// The field will be set to NULL.
				$condition->isNotNull($field);
			}
			else {
				$condition->condition($field, $data, '<>');
				$condition->isNull($field);
			}
		}
		if (count($condition)) {
			$condition->compile($this->connection, $this);
			$this->condition->where((string) $condition, $condition->arguments());
		}
		return parent::execute();
	}

}

/**
 * SQLite specific implementation of DeleteQuery.
 *
 * When the WHERE is omitted from a DELETE statement and the table being deleted
 * has no triggers, SQLite uses an optimization to erase the entire table content
 * without having to visit each row of the table individually.
 *
 * Prior to SQLite 3.6.5, SQLite does not return the actual number of rows deleted
 * by that optimized "truncate" optimization.
 */
class DeleteQuery_sqlite extends DeleteQuery {
	public function execute() {
		if (!count($this->condition)) {
			$total_rows = $this->connection->query('SELECT COUNT(*) FROM {' . $this->connection->escapeTable($this->table) . '}')->fetchField();
			parent::execute();
			return $total_rows;
		}
		else {
			return parent::execute();
		}
	}
}

/**
 * SQLite specific implementation of TruncateQuery.
 *
 * SQLite doesn't support TRUNCATE, but a DELETE query with no condition has
 * exactly the effect (it is implemented by DROPing the table).
 */
class TruncateQuery_sqlite extends TruncateQuery {
	public function __toString() {
		// Create a sanitized comment string to prepend to the query.
		$comments = $this->connection->makeComment($this->comments);

		return $comments . 'DELETE FROM {' . $this->connection->escapeTable($this->table) . '} ';
	}
}

/**
 * @} End of "ingroup database".
 */
